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Efficient homing of antibody-secreting cells to the bone marrow requires RNA-binding protein ZFP36L1.
Cell migration relies on coordinated activity of chemotactic and guidance receptors. Here, we report a specific role for the RNA-binding protein ZFP36L1 in limiting the abundance of molecules involved in the homing of antibody-secreting cells (ASCs) to the bone marrow (BM). In the absence of ZFP36L1, ASCs build up in the spleen and the liver and show diminished accumulation in the BM. ZFP36L1 facilitates migration by directly regulating G protein-coupled receptor kinase 2 (GRK2) and the integrin chains α4 and β1 in splenic ASCs. Expression of CXCR4 and of the integrins α4 and β1 is differentially regulated on ASCs produced at the early and late stages of the immune response. Consequently, deletion of the Zfp36l1 gene has a stronger effect on BM accumulation of high-affinity ASCs formed late in the response. Thus, ZFP36L1 is an integral part of the regulatory network controlling gene expression during ASC homing
Optical Generation and Quantitative Characterizations of Electron-hole Entanglement
Using a method of characterizing entanglement in the framework of quantum
field theory, we investigate the optical generation and quantitative
characterizations of quantum entanglement in an electron-hole system, in
presence of spin-orbit coupling, and especially make a theoretical analysis of
a recent experimental result. Basically, such entanglement should be considered
as between occupation numbers of single particle basis states, and is
essentially generated by coupling between different single particle basis
states in the second quantized Hamiltonian. Interaction with two resonant light
modes of different circular polarizations generically leads to a superposition
of ground state and two heavy-hole excitonic states. When and only when the
state is a superposition of only the two excitonic eigenstates, the
entanglement reduces to that between two distinguishable particles, each with
two degrees of freedom, namely, band index, as characterized by angular
momentum, and orbit, as characterized by position or momentum. The band-index
state, obtained by tracing over the orbital degree of freedom, is found to be a
pure state, hence the band-index and orbital degrees of freedom are separated
in this state. We propose some basic ideas on spatially separating the electron
and the hole, so that the entanglement of band-indices, or angular momenta, is
between spatially separated electron and hole.Comment: 8 pages. Journal versio
Maximally Causal Quantum Mechanics
We present a new causal quantum mechanics in one and two dimensions developed
recently at TIFR by this author and V. Singh. In this theory both position and
momentum for a system point have Hamiltonian evolution in such a way that the
ensemble of system points leads to position and momentum probability densities
agreeing exactly with ordinary quantum mechanics.Comment: 7 pages,latex,no figures,to appear in Praman
A versatile source of polarisation entangled photons for quantum network applications
We report a versatile and practical approach for generating high-quality
polarization entanglement in a fully guided-wave fashion. Our setup relies on a
high-brilliance type-0 waveguide generator producing paired photon at a telecom
wavelength associated with an advanced energy-time to polarisation transcriber.
The latter is capable of creating any pure polarization entangled state, and
allows manipulating single photon bandwidths that can be chosen at will over
five orders of magnitude, ranging from tens of MHz to several THz. We achieve
excellent entanglement fidelities for particular spectral bandwidths, i.e. 25
MHz, 540 MHz and 100 GHz, proving the relevance of our approach. Our scheme
stands as an ideal candidate for a wide range of network applications, ranging
from dense division multiplexing quantum key distribution to heralded optical
quantum memories and repeaters.Comment: 5 figure
The impact of genetic selection on greenhouse-gas emissions in Australian dairy cattle
In Australia, dairy cattle account for ~12% of the nation’s agricultural greenhouse-gas (GHG) emissions. Genetic selection has had a positive impact, reducing GHG emissions from dairy systems mainly due to increased production per cow, which has led to (1) requiring fewer cows to produce the same amount of milk and (2) lowering emissions per unit of milk produced (emission intensity). The objective of the present study was to evaluate the consequences of previous and current genetic-selection practices on carbon emissions, using realised and predicted responses to selection for key traits that are included in the Australian national breeding objective. A farm model was used to predict the carbon dioxide equivalent (CO₂-eq) emissions per unit change of these traits, while holding all other traits constant. Estimates of the realised change in annual CO₂-eq emissions per cow over the past decade were made by multiplying predicted CO₂-eq emissions per unit change of each trait under selection by the realised rates of genetic gain in each of those traits. The total impact is estimated to be an increase of 55 kg CO₂-eq/cow.year after 10 years of selection. The same approach was applied to future CO₂-eq emissions, except predicted rates of genetic gain assumed to occur over the next decade through selection on the Balanced Performance Index (BPI) were used. For an increase of AU100). In fact, cow numbers have decreased over the past decade and production has increased; altogether, we estimate that the net impact has been a reduction of CO₂-eq emissions of ~1.0% in total emissions from the dairy industry per year. Using two future scenarios of either keeping the number of cows or amount of product static, we predict that net GHG emissions will reduce by ~0.6%/year of total dairy emissions if milk production remains static, compared with 0.3%/year, if cow numbers remain the same and there is genetic improvement in milk-production traits
Gamma Rays and Neutrinos from SNR RX J1713.7-3946
The supernova paradigm for the origin of galactic cosmic rays can be tested
using multifrequency observations of both non-thermal and thermal emission from
supernova remnants. The smoking gun of hadronic acceleration in these sources
can, however, only be provided by the detection of a high energy neutrino
signal. Here we apply the theory of non-linear particle acceleration at
supernova shocks to the case of the supernova remnant RX J1713.7-3946, which is
becoming the stereotypical example of a possible hadronic accelerator after the
detection of high energy gamma rays by the HESS telescope. Our aim is twofold:
on one hand we want to address the uncertainties in the discrimination between
a hadronic and a leptonic interpretation of the gamma ray emission, mainly
related to the possibility of a statistical uncertainty in the energy
determination of the gamma ray photons in the TeV region. On the other we want
to stress how a km cube neutrino telescope would break the degeneracy and
provide evidence for efficient cosmic ray acceleration in RX J1713.7-3946. A 3
sigma evidence would require about two years of observation.Comment: 11 pages, 3 figures, accepted for publication in Astropaticle Physic
A trio of new Local Group galaxies with extreme properties
We report on the discovery of three new dwarf galaxies in the Local Group.
These galaxies are found in new CFHT/MegaPrime g,i imaging of the south-western
quadrant of M31, extending our extant survey area to include the majority of
the southern hemisphere of M31's halo out to 150 kpc. All these galaxies have
stellar populations which appear typical of dwarf spheroidal (dSph) systems.
The first of these galaxies, Andromeda XVIII, is the most distant Local Group
dwarf discovered in recent years, at ~1.4 Mpc from the Milky Way (~ 600 kpc
from M31). The second galaxy, Andromeda XIX, a satellite of M31, is the most
extended dwarf galaxy known in the Local Group, with a half-light radius of r_h
~ 1.7 kpc. This is approximately an order of magnitude larger than the typical
half-light radius of many Milky Way dSphs, and reinforces the difference in
scale sizes seen between the Milky Way and M31 dSphs (such that the M31 dwarfs
are generally more extended than their Milky Way counterparts). The third
galaxy, Andromeda XX, is one of the faintest galaxies so far discovered in the
vicinity of M31, with an absolute magnitude of order M_V ~ -6.3. Andromeda
XVIII, XIX and XX highlight different aspects of, and raise important questions
regarding, the formation and evolution of galaxies at the extreme faint-end of
the luminosity function. These findings indicate that we have not yet sampled
the full parameter space occupied by dwarf galaxies, although this is an
essential pre-requisite for successfully and consistently linking these systems
to the predicted cosmological dark matter sub-structure.Comment: 32 pages, 7 figures (ApJ preprint format). Accepted for publication
in Ap
The structural properties and star formation history of Leo T from deep LBT photometry
We present deep, wide-field g and r photometry of the transition type dwarf
galaxy Leo T, obtained with the blue arm of the Large Binocular Telescope. The
data confirm the presence of both very young (5
Gyr) stars. We study the structural properties of the old and young stellar
populations by preferentially selecting either population based on their color
and magnitude. The young population is significantly more concentrated than the
old population, with half-light radii of 104+-8 and 148+-16 pc respectively,
and their centers are slightly offset. Approximately 10% of the total stellar
mass is estimated to be represented by the young stellar population. Comparison
of the color-magnitude diagram (CMD) with theoretical isochrones as well as
numerical CMD-fitting suggest that star formation began over 10 Gyr ago and
continued in recent times until at least a few hundred Myr ago. The CMD-fitting
results are indicative of two distinct star formation bursts, with a quiescent
period around 3 Gyr ago, albeit at low significance. The results are consistent
with no metallicity evolution and [Fe/H] ~ -1.5 over the entire age of the
system. Finally, the data show little if any sign of tidal distortion of Leo T.Comment: 8 pages, 9 figures, some small textual changes, accepted for
publication in the Astrophysical Journa
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